This document describes 9 qualitative tests for carbohydrates: 1) Molish test detects carbohydrates using alpha-naphthol which produces a purple color. 2) Anthrone test uses anthrone reagent to detect sugars and produces a blue-green color. 3) Benedict's test detects reducing sugars using a copper sulfate solution that forms a red precipitate. 4) Picric acid test also detects reducing sugars, forming a red color. 5) Bial's test detects carbohydrates using orcinol and ferric chloride, producing a blue color. 6) Iodine test detects carbohydrates, changing color when mixed with iodine. 7) Borfoed's test detects reducing

1. Desh Bandhu Gangwar
M.Tech (BT) 2 year
QUALITATIVE TESTS FOR CARBOHYDRATES
1)Molish Test
Reagents:
 Conc. H2SO4 (Sol A)
 5 gm α-nepthol in 100 ml ethanol (Sol B), prepare fresh
Protocol:
2ml test solution
Add 2-3 drop of sol B
Pipette 1ml sol. A gently along the side of test tube
Observe change of colour at the junction of two layer
Appearance of purple colour indicates +ve test
10/pbt/006

2. 2) Anthrone Test
Reagents:
 Conc. H2SO4 (Sol A)
 0.2% anthrone solution in con.H2SO4 (Sol B)
Protocol:
0.5 to 1 ml test solution
Add 2ml of sol B
Through mixing
Observe change in colour
Appearance of bluish green colour +ve test
If not, boil in water bath for 10 min
Appearance of bluish green colour
10/pbt/006

3. 3) Bendict’s Test
Reagents:
 173 gm. Sodium citrate and 100 gm anhydrous Na2CO3 In
600 ml hot distilled water (Sol A) {bendict’s reagent}
 17.3 gm copper sulphate in 100 ml hot distilled water (Sol B)
 Add sol A and sol B in 1:1, make final vol. 1 lit (sol C)
Protocol:
0.5ml test sol
Add 2ml of sol C
Through mixing
Cook in water bath
Observe formation of red ppt.
Presence of reducing sugar
10/pbt/006

4. 4) Picric Acid Test
Reagents:
 13% picric acid w/v in DW, boil and cool (Sol A)
 10% Na2CO3 (Sol B)
Protocol:
1 ml test solution
Add 1ml of sol A & 0.5 ml of sol B
Cook in water bath
Observe formation of red colour
Presence of Reducing sugar
10/pbt/006

5. 5) Bial’s Test
Reagents:
 1.5 gm orcinol in 100 ml con. Hcl (sol A)
 10% Fecl3 solution (sol B)
 Add 20 to 30 drops of sol B into sol A (sol C)
Protocol:
4 to 5 drops of test solution
Add 2ml of sol C
Cook in water bath
Observe formation of bluish colour
Presence of carbohydrate
10/pbt/006

6. 6) Iodine Test
Reagents:
 0.005 N I2 in 3% KI (Sol A)
Protocol:
0.5 to 1 ml test solution
Add 4 to 5 drops of sol A
Gentle mixing
Observe change in colour
10/pbt/006

7. 7) Borfoed’s Test
Reagents:
 13.3 gm copper acetate in 200 ml DW (sol A)
 1.80 ml glacial acetic acid (Sol B)
 Mix sol A & sol B (barfoed reagent) (sol C)
Protocol:
1 ml test solution
Add 2ml sol C
Cook in boiling water bath
Observe formation of brick red colour
10/pbt/006

8. 8) Seliwanoff’s Test
Reagents:
 0.05% w/v resorcinol in 3N HCl (sol A)
Protocol:
take 1 ml test solution
Add 2ml sol A
Cook in boiling water bath for 1 min
Observe formation of deep red colour
Presence of ketose sugar
10/pbt/006

9. 9) Fehling’s Test
Reagents:
 35.0 gm copper sulphate in DW in 500 ml (sol A)
 120 gm KOH and 173 gm Na-K tartarate in 500ml water (sol B)
 Mix sol A+ sol B in 1:1 ratio (sol C)
Protocol:
take 1 ml of test solution
Add 1 ml sol C
mix thoroughly
Cook in water bath
Observe formation of red ppt.
Presence of reducing sugar
10/pbt/006